1. Field of the Invention
The present invention relates to a colored curable composition for a color filter, a color filter and a method for producing the same, and a solid state imaging device.
2. Description of the Related Art
Liquid crystal display devices (such as LCDs) and solid state imaging devices (such as CCDs and CMOSs) have color filters having colored areas of, for example, red (R), green (G), and blue (B). The color filter is generally produced by forming a colored pattern by applying a colored curable composition onto a support.
In order to form the colored pattern, a method of patterning a colored photosensitive composition utilizing a photolithography method has been widely employed, the colored photosensitive composition containing a pigment that is dispersed in any of various photosensitive compositions by, for example, a pigment dispersion method. In a specific example of the production of a color filter, a colored photosensitive composition is applied onto a substrate by, for example, a spin coater or a roll coater to form a coating film, and pattern-exposing and developing the coating film to form a colored pattern, and this process is repeated for a number of times corresponding to the number of the desired hues. According to the method, since the photolithography method is used, the positional accuracy is high. Therefore, the method is suitable for producing color filters having a big screen and a high resolution.
In recent years, the thickness of the colored pattern of the color filter have been reduced and the resolution thereof have been increased, which is expected to improve the color density or the color tone. Moreover, the size of the colored pattern has also been decreased. These trends are particularly remarkable in color filters for solid state imaging devices. In the color filters for solid state imaging devices, the reduction in the thickness (e.g., to a thickness of 1 μm or less) of the colored pattern has been in demand particularly from the viewpoint of improving the image quality through higher light gathering properties and improved light color separation properties. In order to reduce the thickness thereof, it is necessary to increase the concentration of a coloring material in consideration of color density. However, an increase in the concentration of a coloring material remarkably reduces the sensitivity, as a result of which the pattern is likely to detach at a low exposure range.
These filter properties of the color filters are influenced by the exposure sensitivity during exposure treatment, pattern shape, development residue, adhesiveness to a substrate, and the like in many cases, and the exposure properties of the composition in an exposure stage before development treatment are important factors. As one of the methods for improving such exposure properties, various studies on initiators have been conducted, and the selection of initiators or a method for increasing the amount thereof is known.
For example, Japanese Patent Application Laid-Open (JP-A) No. 2005-316012 discloses, as a technique relevant to the above, a radiation-sensitive resin composition for forming a colored layer using an α-amino alkyl phenone-based photopolymerization initiator with a polyfunctional monomer in consideration of development properties, pattern shape, and the like when forming a colored layer of a color filter.